With wide spread of Personal Computer (PC) services and smart User Equipment (UE), there is an increasingly high requirement on wireless communication experience, and in particular a communication rate. In a Long Term Evolution (LTE) standard and subsequent standard evolution, to enhance user perception and a system throughput, in particular to increase hotspot throughput, a networking architecture of Heterogeneous Networks (HetNet) is adopted, namely, a number of small cells are deployed within a coverage area of a Macro cell to enhance hotspot serving quality and throughput.
Although effective for increasing network capacity and reducing a coverage blind area, increasing a number of small cell nodes deployed in a hotspot may at the same time lead to a number of problems such as mutual interference, handover, energy consumption, and the like in an application scene with densely deployed small cells. Therefore, a small cell may be turned on when there is a system capacity increasing demand; and may be turned off when there is no additional capacity increasing demand and UE connection to reduce interference to an adjacent small cell and power consumption. When a UE is connected to another small cell (or the Macro cell), for mobility and network management purposes, it is necessary to discover another non-serving small cell. An effective solution for this may be to have a small cell node send a Discovery Signal (DS). A UE receives the DS and reports discovering and measuring information for determining whether to activate the small cell. Given interference and power consumption the DS may result in, it is unlikely to have a very short DS sending period.
FIG. 1 is a diagram of a typical small cell scene. As shown in FIG. 1, two small cells may work on a same frequency; and a Macro cell and a small cell may work on different frequencies or may work on a same frequency. A coverage area of the Macro cell may be within a thick-solid-line circle. A coverage area of a Small cell 1 may be within a thin-dashed-line circle. A coverage area of a Small cell 2 may be within a thin-solid-line circle.
In condition 1, when no UE is connected within the coverage area of the Small cell 1, the Small cell 1 may be in a sleep or shutdown state and send a DS. In this case, both UE1 and UE2 may be served by the Small cell 2. When the UE 1 and the UE 2 move from the Small cell 2 toward the Small cell 1 and successively enter the coverage area of the Small cell 1, the UE 1 may take the lead to detect the DS sent by the Small cell 1 and report discovering and measuring information. Meanwhile, the UE 2 may be yet to detect the DS sent by the Small cell 1. Therefore, the Small cell 1 knows that the UE 1 is within the coverage area per se without knowing the UE 2. In this case, both UE 1 and UE 2 remain being served by the Small cell 2. In this case, when the Small cell 1 enters an activated state, the Small cell 1 may result in strong interference to the UE 2 yet to discover the DS sent by the Small cell 1. In short, premature activation of a small cell in a deactivated state may result in strong interference to a UE in an adjacent cell.
In condition 2, after the Small cell 1 has served the UE 1 for a period of time, the UE 1 leaves the coverage area of the small cell, and no other UE is served within the Small cell 1. The Small cell 1 may sleep or shut down. However, when the UE 1 again returns to the coverage area of the Small cell 1, the Small cell 1 may reenter the activated state. When the UE 1 goes back and forth between the two small cells, the Small cell 1 may switch between the deactivated state and the activated state frequently, thus leading to constantly changing and fluctuating interference of the Small cell 1 to an adjacent cell. In short, when a small cell in the activated state enters a sleep state too early (premature sleep), this may result in fluctuating interference to a UE in an adjacent cell.